Hot work

Risks of hot work

A fire requires fuel, an oxidizer, and an ignition source. Hot work provides controlled ignition energy (flame, sparks, incandescent particles that can be projected several meters, hot surfaces, electric arc), so the risk depends on the surrounding environment: combustible materials (packaging, insulation, dust, waste, liquids), flammable atmospheres (solvent vapors, gases, airborne dust), waste in supposedly empty tanks or pipes, and gaps, ducts, and false ceilings through which sparks can travel to unsupervised areas.

Added to this are the risks to the operator: burns, ultraviolet and infrared radiation in welding, welding fumes (metal oxides, ozone, nitrous gases) with respiratory and carcinogenic effects in certain alloys, electrical contact, projection of particles, noise, explosion of bottles and flashback in oxyacetylene equipment, and asphyxiation or poisoning in confined spaces due to oxygen consumption and accumulation of gases.

Royal Decree 681/2003 prohibits ignition sources in areas classified as having a risk of explosive atmospheres, except with specific authorization and control measures, and Royal Decree 486/1997 requires that workplaces have adequate fire protection measures. INSST Technical Standards 30 and 562 describe permits for special work, including hot work, and Standards 494 and 495 cover safety regulations for electric and oxyacetylene welding .

Preventive measures and the hot work permit

• Avoid hot work. Consider alternatives: cold mechanical cutting, bolted or adhesive joints, prefabrication in the workshop, and transfer of the part to a safe welding area.
• Work permit. Written authorization, with limited validity in time and place, which identifies the task, the risks of the environment, the measures required, the person responsible for issuing it, the person carrying it out and the fire watchman, and which is closed with a final check.
• Area preparation. Remove or protect fuels within a suitable radius (usually 10 meters or more depending on the task), cover openings, ducts and gaps, dampen combustible floors where appropriate, and clean up debris and dust.
• Atmosphere control. Measurement of flammable gases and vapors with an explosimeter before and during work in risk areas, forced ventilation, emptying, cleaning and inerting of tanks and pipes, and prohibition of working in explosive atmospheres.
• Extinguishing means. Suitable fire extinguishers on hand, fire blankets, fire hydrants available and verification that detection systems are not disabled without control or are reset upon completion.
• Fire watchman. Person dedicated to monitoring during work and for a period afterwards (frequently between 30 and 60 minutes, depending on the assessment) to detect latent fires, with extinguishing and communication equipment.
• Equipment and PPE. Welding and cutting equipment maintained, non-return valves, clamps and cables in good condition, and appropriate PPE: welding screen, flame-resistant clothing, gloves, respiratory and hearing protection as appropriate.
• Welding fumes. Local exhaust ventilation and respiratory protection; consideration of the carcinogenic risk of certain fumes in accordance with Royal Decree 665/1997.

Situations of special risk

• Tanks, reservoirs, and pipes. Containers that have held flammable materials retain vapors; they require emptying, cleaning, ventilation, measurement, and inerting before any hot work.
• Confined spaces. Hot work in confined spaces combines fire risk , oxygen consumption and smoke accumulation; it requires joint permit, forced ventilation, continuous measurement and external monitoring.
• Roofs and insulation. Fireproofing and welding on roofs with combustible insulation or sandwich panels, the source of numerous industrial fires.
• ATEX zones. Work in classified areas only with specific authorization, elimination of the explosive atmosphere and continuous monitoring.
• Contractors. Hot work carried out by external companies requires coordination of activities, information on the risks of the center and application of the owner’s permit system.
• Construction and maintenance. During construction and maintenance shutdowns, the simultaneous nature of tasks and the presence of combustible materials increase the risk; the safety plan and coordination must take this into account.

Organizational application: how to manage hot work

1. Define in the procedure which operations are considered hot work and in which areas they require permission, distinguishing between permanent welding areas and work in unprepared areas.
2. Implement the hot work permit with issuing officers, a checklist of measures, limited validity, a fire watchman, and closure with final verification.
3. Evaluate each job with attention to the environment: fuels, flammable atmospheres, ducts and gaps, tanks and pipes, detection and extinguishing systems.
4. Provide adequate fire extinguishing equipment, gas measurement, ventilation and PPE, and maintain welding and cutting equipment.
5. Train the enforcers, the permit issuers and the fire watchmen, and require the same training for contractors.
6. Integrate hot work into the coordination of business activities and the emergency plan.
7. Record the permits and incidents and analyze them to review the procedure.

Preventive management software allows you to manage hot work permits with issuance, verification and closure workflows, record measurements and monitoring, link contractors and their accreditations and maintain traceability of each intervention.

Limits and common mistakes

1. Performing hot work without permission because it is considered brief or routine.
2. Do not remove or protect fuels from the surroundings, nor cover gaps and conduits through which sparks propagate.
3. Welding or cutting in supposedly empty tanks or pipes without draining, cleaning, venting and measuring.
4. Dispensing with the fire watchman or ending the watch immediately upon completion of the work, without controlling latent sources of fire.
5. Disabling fire detection systems during work without control or documented replacement.
6. Ignoring welding fumes and working without local exhaust ventilation or respiratory protection.

Specific obligations are set out in the regulations on workplaces, explosive atmospheres, work equipment, carcinogenic agents and fire safety; this sheet is for informational purposes.

Regulatory and reference framework

• Law 31/1995, of November 8. Law on the Prevention of Occupational Risks; risk assessment, emergency measures and coordination of business activities.
• Royal Decree 486/1997, of April 14. Workplaces ; fire protection and safety conditions.
• Royal Decree 681/2003, of June 12. Protection of workers exposed to risks arising from explosive atmospheres; control of ignition sources.
• Royal Decree 164/2025, of March 4. Fire safety regulations in industrial establishments, which repeals Royal Decree 2267/2004.
• NTP 562: Preventive management system: authorizations for special work (INSST) . Work permits, including hot work.
• NTP 494: Electric arc welding: safety standards (INSST) . Risks and measures in electric welding.
• NTP 495: Oxyacetylene welding and oxyfuel cutting: safety standards (INSST) . Risks and measures in oxyacetylene welding and oxyfuel cutting.

Royal Decree 1215/1997 regulates the use of welding and cutting equipment, Royal Decree 665/1997 regulates exposure to carcinogenic agents present in certain welding fumes, and INSST NTP 30 regulates special work permits.